Former education secretary Justine Greening has ruled herself out of the race to become the next mayor of London. 

The Tory MP for Putney had been tipped as the likely Conservative candidate to battle Labour’s Sadiq Khan for the City Hall top job after favourite Ed Vaizey endorsed her.

But, in a tweet on Wednesday night, Greening said she would be focusing on a national social mobility project instead. 

She said: “Thanks @JustineForMayor – all your support is hugely appreciated, but as an MP I’m focusing on socialmobilitypledge.org to drive opportunity for people across our whole country so won’t be putting my name forward.” 

The Conservatives are set to begin the process of selecting a candidate this month with a final vote due in September. 

Other potential candidates for the job include Brexiteer MEP Syed Kamall, London Assembly member Shaun Bailey, who has been a vocal critic of Khan’s handling of the knife crime epidemic, former MP Nick Du Bois and Evening Standard editor and former chancellor George Osborne.

The timetable is designed to give the party a two-year run at beating Khan, who remains popular with the public. 

Zac Goldsmith, who was selected the September before the May 2016 vote, is seen as having little time to establish himself. 

The Richmond MP’s campaign, run by Sir Lynton Crosby, attracted criticism for “dog whistle” xenophobic tactics against Khan.